PROJECT SUMMARY Higher levels of physical activity have been found to improve health and to reduce cognitive decline as adults become older, but more than half of all adults in the United States do not meet their activity goals. Regular physical activity is associated with numerous health benefits and one type of physical activity that is broadly applicable to people of all ages is walking. Programs to increase walking are both broadly feasible and safe, and do not require unique training or specialized equipment. Walking is also measurable, with clearly identifiable individual targets that are associated with health improvements. This study will use a Hybrid Type 1 effectiveness-implementation design to adapt, and test the effectiveness of, two successful social incentive-based interventions to increase physical activity. Social incentive-based interventions can harness and enhance an individual's social network to increase physical activity, and can be more sustainable and scalable than financial incentives. The two interventions are a gamification strategy and financial incentives donated to charity on the participant's behalf. Following an initial phase of community-participatory adaptation of the two proven social-incentive intervention strategies, a three-arm, cluster-randomized trial of 225 families will be conducted to evaluate the two social incentive interventions in the community. The study aims include: 1. To adapt our prior work to improve the implementation of interventions in the community among families that include at least one older adult. 2. To evaluate the effectiveness of two social-incentive interventions among families to increase physical activity relative to control families. 3. To conduct a robust process evaluation that will provide information on the implementation process. 4. To assess the cost of each of the interventions from a societal perspective and compare cost differences between each intervention and control relative to the effectiveness measured by incremental increases in physical activity. 5. To use findings from the effectiveness trial, process evaluation and cost analysis (Aims 2, 3 and 4) to scale-up and disseminate tools and products for use by community organizations locally and nationally. This study focuses on scalable approaches to address health disparities in physical activity by partnering with community organizations in low-income and minority neighborhoods, using behavioral economics to deploy low-cost social incentive interventions, and applying implementation science frameworks from the Consolidated Framework for Intervention Research (CFIR) to improve adoption and dissemination. An effectiveness-implementation study design will maximize contributions to science, public health practice, and reduction of health disparities.